Many describe using nails in a street fight the woman's way of fighting. However, does that mean it won't work? Would you use your nails in a street fight? Usually if you use your nails to strike, you might be able to cut your attacker. However you might break a nail in the process which can be somewhat painful as well.
I think I would use mine in grappling. Every grip I make I would use my nails and sink it into whatever move (armbar, choke, ect.) I am doing. I don't think I would use it strike, because breaking a nail might not be the wisest (well that is if your life is not at stake, then it is maybe okay).
Also does anyone in hear sharpen their nails just for self-defense? Sound strange to me, but it might no be a bad idea.